The STF8N90K5: The 900 V drain-to-source rating gives you a solid derating margin for universal-input offline designs that see transient spikes up to 800 V or more. That saves assembly time and improves thermal transfer in a crowded chassis.
Temperature range and gate threshold — the bench reality
Maximum gate threshold voltage is 5 V at 100 µA drain current. 10 V gate drive needed for lowest Rds(on). ±30 V maximum gate-source rating.
Active lifecycle. 900 V drain-source. 8 A continuous drain current.